1. Technical Field
This invention generally relates to an apparatus and method for identifying people with attentional disorders based upon a low sensory arousal system by obtaining and processing electroencephalographic information and applying that data to an algorithm to differentiate between low sensory attentional disorders and other, affective type, disorders.
2. Background
In the field of child and adolescent psychiatry, Attention-Deficit/Hyperactivity Disorder, originally known as minimal brain dysfunction, has been theorized to be of a neurobiological nature. The predominant view is that cognitive and behavioral deficits exhibited with this disorder are the consequences of brain dysfunction although the exact etiology and biological substrata such as lowered levels of reticular activating system excitation which results in low cortical arousal, cortical immaturity or delayed maturation and/or attention-inhibition deficits is not known with any degree of certainty.
There are a number of attentional disorders based upon a low sensory arousal system. Perhaps the best known, and most common of these is Attention-Deficit/Hyperactivity Disorder, for which a definition is found in the American Psychiatric Association Diagnostic and Statistical Manual of Mental Disorders. It states: xe2x80x9c[t]he essential feature of Attention-Deficit/Hyperactivity Disorder is a persistent pattern of inattention and/or hyperactivity-impulsivity that is more frequent and severe than is typically observed in individuals at a comparable level of development. . . . There must be clear evidence of interference with developmentally appropriate social, academic, or occupational functioning. . . . The disturbance does not occur exclusively during the course of a Pervasive Developmental Disorder, Schizophrenia, or other Psychotic Disorder and is not better accounted for by another mental disorder (e.g. a Mood Disorder, Anxiety Disorder, Dissociative Disorder, or Personality Disorder. . . . xe2x80x9d Attention-Deficit/Hyperactivity Disorder is also found in those suffering from other Attentive Disorders such as obsessive compulsive disorders, bi-polar disorders, rumination disorders, manic and hypo-manic disorders, and depression.
Some disorders, such as rumination in conjunction with obsessive/compulsive and manic disorders are often misdiagnosed as strictly Attention-Deficit/Hyperactivity Disorder. When misdiagnosed as Attention-Deficit/ Hyperactivity Disorder, individuals may be erroneously prescribed stimulant medications. Stimulant medications for those suffering from obsessive/compulsive, bi-polar and manic disorders is not appropriate, and results in the individual becoming extremely tired and will increase the aggressive, agitated rebound effect in the evenings when the stimulants wear off. When a hypo-manic suffering from rumination is misdiagnosed as Attention-Deficit/Hyperactivity Disorder and given stimulant medication, the patient is put at risk psychiatrically and educationally. In effect, it is the misdiagnosis and incorrectly prescribed stimulant which may exacerbate psychotic symptoms or actually induce psychosis. In academic environments, such as children at school, such individuals may be more behaviorally compliant, and still suffer decreased cognitive retention, leading to diminished learning potential. In such cases, parents and teachers will typically know that the stimulation medication is not perfect, but is still better than nothing. However, when properly diagnosed, individuals, particularly children suffering from obsessive-compulsive, bi-polar or manic disorders exhibiting ruminating behavior, can be treated effectively.
Accordingly, it is an object of the present invention to provide an apparatus and method for identifying whether a person is experiencing: solely an attention disorder based upon a low sensory arousal system; other, attentive type, disorders; or a combination of low sensory system attention disorder and other attentive disorders, and thus to more accurately segregate and appropriately treat these individuals.
These objects are achieved using a testing apparatus which includes an EEG Data Acquisition and Analysis System, which is electrically interconnected to a head assembly containing a plurality of EEG electrodes. The output from the EEG Data Acquisition and Analysis System is sent to a microprocessor where two primary functions of the testing system are performed. These are, the quantification of a standard EEG into absolute powers in the delta, theta, alpha and beta frequency bands and the timing, synchronization and averaging of a series of displays of a paradigm generating a visually evoked response.
Also electrically interconnected to the microprocessor is a visual display device for periodically displaying a plurality of sequential, visual paradigms to a test subject. Hard copy output devices, such as a printer and/or a video output are also interconnected to the microprocessor.
In use, the testing system is used to identify the type of attention disorder an individual is afflicted with. The individual to be tested is first seated comfortably in a chair and sixteen (16) electrodes are attached to the scalp of the individual to be tested in accordance with the International 10-20 System of the American Electroencephalographic Society""s guidelines, namely to locations F7, F3, F4, F8, T3, C3, CZ, C4, T4, T5, P3, PZ, P4, T6, 01 and 02. Electrode impedance is maintained at less than 2.0 kilo-ohms and the impedance between homologous sites maintained within 1.0 kilo-ohms. The gain for the EEG Data Acquisition and Analysis System is set at 30,000, with a low pass filter at 100 Hz, and a high pass filter at 1.0 Hz, and a 60 Hz notch filter is set in.
A standard quantitative electroencephalogram is then performed, at which time the EEG Data Acquisition and Analysis System, working in conjunction with the microprocessor, provides a measurement as to the absolute power of the electroencephalograph in the delta, theta, alpha and beta frequency bands, all in the absence of any visual or auditory stimulus.
Next, a visually evoked potential test is conducted using a visual checkerboard pattern reversal and a flash paradigm displayed on the visual device at eye level, 76 cm in front of the individual being tested. The pattern is reversed every 0.59 seconds for a total of 1.7 stimuli per second. A 256 and a 512 millisecond (ms) epoch is utilized with a five millisecond pre-stimulus time. The intensity of the background stimulus is 12.69 candelas per square meter, and the flash is 19.26 candelas per square meter. The test subject is instructed to visually fixate on a red dot centered on the visual device, is requested not to speak, and to remain relaxed with as little movement as possible throughout the two minutes of recording time.
The visually evoked response to each display of a paradigm, as recorded by the EEG Data Acquisition and Analysis System, is then recorded in the microprocessor in a synchronized manner with the time of the display of the paradigm and then averaged together to cancel out the potentials of brain activities that are not related to the visually evoked response, thus generating, in microvolts, the potential of the visually evoked response over a period of time from immediately prior to the display of the paradigm to the time of approximately 500 milliseconds after cessation of the displayed paradigm.
Next, the theta-to-beta ratio, as taken at the electrode placement location CZ is computed. Then the maximum positive voltage potential, in microvolts, of the visually evoked response at a time of approximately 100 milliseconds after cessation of the displayed visual checkerboard paradigm as averaged as previously described is measured at the O1 and O2 electrode sites, said maximum measurement is hereinafter defined as the P100MAX value. And finally, the maximum positive voltage potential, in microvolts, of the visually evoked flash response at a time of approximately 200 milliseconds after cessation of the displayed visual paradigms, is measured at the F3 and F4 electrode sites, said maximum measurement is hereinafter defined as the P200MAX value.
An algorithm is then applied to this data. If the theta-to-beta ratio is equal to, or greater than four, indicating an excess of slow wave activity, the person tested is identified as having a low sensory attentional disorder. If the theta-to-beta ratio is less than four then the person tested is identified as having some other, attentive type, disorder.
Next, in the case of the person identified as having an existing low sensory attentional disorder, if the maximum positive voltage potential of the P100MAX wave is less than 10.0 microvolts (xcexcV), and the maximum positive voltage potential of the P200MAX wave is less than 6.0 xcexcV, the person may be identified as having only a low sensory attentional disorder. If either the P100MAX is 10 xcexcV or greater, or P200MAX is 6 xcexcV or greater, the person tested is identified as having a low sensory attentional disorder and at least one other affective disorder. The other specific affective disorder, or disorders, may then be identified based upon comorbid affective components using other diagnostic techniques known in the prior art.
In the case of the person identified as not having an existing low sensory attentional disorder, if the maximum positive voltage potential of the P100MAX wave is less than 10.0 xcexcV, and the positive voltage potential of the P200MAX wave is less than 6 xcexcV, the person may be identified as having only one affective disorder, probably depression. If either the P100MAX is 10 xcexcV or greater, or P200MAX is 6 xcexcV or greater, the person tested is identified as suffering from at least one other affective disorder and possibly more. Again known prior art diagnostic techniques may be used to evaluate the comorbid affective components exhibited by the person tested.